From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751677AbdKVQTK (ORCPT ); Wed, 22 Nov 2017 11:19:10 -0500 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:41178 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751303AbdKVQTJ (ORCPT ); Wed, 22 Nov 2017 11:19:09 -0500 Date: Wed, 22 Nov 2017 17:19:07 +0100 From: Pavel Machek To: Dave Hansen Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 00/23] KAISER: unmap most of the kernel from userspace page tables Message-ID: <20171122161907.GA12684@amd> References: <20171031223146.6B47C861@viggo.jf.intel.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="vtzGhvizbBRQ85DL" Content-Disposition: inline In-Reply-To: <20171031223146.6B47C861@viggo.jf.intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --vtzGhvizbBRQ85DL Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi! > KAISER makes it harder to defeat KASLR, but makes syscalls and > interrupts slower. These patches are based on work from a team at > Graz University of Technology posted here[1]. The major addition is > support for Intel PCIDs which builds on top of Andy Lutomorski's PCID > work merged for 4.14. PCIDs make KAISER's overhead very reasonable > for a wide variety of use cases. Is it useful? > Full Description: >=20 > KAISER is a countermeasure against attacks on kernel address > information. There are at least three existing, published, > approaches using the shared user/kernel mapping and hardware features > to defeat KASLR. One approach referenced in the paper locates the > kernel by observing differences in page fault timing between > present-but-inaccessable kernel pages and non-present pages. I mean... evil userspace will still be able to determine kernel's location using cache aliasing effects, right? Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --vtzGhvizbBRQ85DL Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAloVo3sACgkQMOfwapXb+vIG4ACeOWzVb819E5m4e8mS0CQU2u35 xeQAn1Nj43UAPZWfdEGY4tlyVYRxIUr4 =dxs0 -----END PGP SIGNATURE----- --vtzGhvizbBRQ85DL--